Trucks, trailers, containers and railway cars employed in the transportation of goods requiring refrigeration, e.g., frozen foods, or heat, consist generally of an insulated, enclosed compartment and a refrigeration unit which supplies cold air or heat to the compartment. To maintain the proper temperature at all of the cargo carried within the compartment, it is necessary to circulate cold or heated air beneath the cargo, as well as around its sides and top. To achieve this air circulation, the floors of such compartments are generally formed with air passages below the load carrying surfaces, such that air can flow below the cargo resting on the floor.
In one common configuration of such a floor, the floor is made up of a number of interconnecting panels, each of which consists of a generally flat base from which a plurality of parallel-spaced T-shaped members extend upwardly, the horizontal top flanges of the members all lying in the same plane to support the goods being carried. The spaces between the parallel T-shaped rails or members allow for good air circulation beneath the goods. However, this type of floor structure is limited in load carrying capacity, and is subject to crumpling under heavy stresses, such as may be imposed upon it by a forklift or similar loading vehicle entering the compartment, or dropping of a heavy crate. Moreover, because of the horizontal flanges, loose pieces of the cargo and scraps of other material tend to catch under and wedge between the T-shaped members, making cleaning of the floor difficult.
Another commonly used floor construction for refrigerated cargo compartments is made up of interconnecting panels, each of which is formed with a plurality of parallel-spaced inverted U-shaped channel members. Because of the box-like configuration of the inverted U-channels, this type of floor provides better structural strength than the floor formed of T-shaped members, but suffers the disadvantage that air flow beneath the cargo being carried is limited, since no air can circulate effectively beneath the horizontal load bearing surfaces of the inverted U-shaped channels.
Efforts have been made in the past to mitigate the respective disadvantages of the T-shaped and U-shaped floor sections discussed above. Thus, as described in U.S. Pat. No. 3,416,280 to Young, contoured inserts are slipped in between the T-shaped members of the floor construction to add rigidity where needed. The constructions shown in U.S. Pat. Nos. 3,128,851 to DeRitter et al, and 4,019,743 to Lemmon, employ relatively narrow U-shaped channels topped with horizontal flanges in an effort to overcome the advantages of the T-shaped members and the inverted U-shaped channels when used alone. However, neither avoids all of the disadvantages enumerated above and, furthermore, are more complex and expensive to manufacture than simple T-shaped or U-shaped floor sections.